Transition metal base olefin polymerization catalysts, when first developed, were employed under low pressure conditions in solvents or liquid diluents under solution or slurry polymerization process conditions. Later advances in the art of olefin polymerization technology allowed some of such catalysts to be used in low pressure gas phase processes which employed very little, if any, solvent or liquid diluent. In order to be used in such low pressure gas phase processes the various types of catalysts had to be adapted in various ways so as to allow them to function catalytically in a practical manner in these new processes. Although various catalyst modification techniques have been employed, such as the use of various types of supports, for facilitating the use of these catalysts in the various types of gas phase processes, it has been found necessary to further modify the known components of these catalyst systems to enable such catalyst systems to be used in a facile manner in fluidized bed processes in order to provide currently desired commercial results in the polymer products.
U.S. Pat. Nos. 4,048,415; 4,135,045 and 4,296,222 disclose that olefin polymerization catalyst components that may be used under low pressure conditions may be ball milled or micropolymerized to provide useful forms of transition metal based catalysts without the use of supports for the catalysts. U.S. Pat. No. 3,718,635 discloses the use of a ball milled supported low pressure olefin polymerization catalyst which has been supported on certain metal oxide supports. The catalysts of these patents are all intended to be used in the presence of inert solvent or liquid diluent.
Canadian Pat. No. 1,144,300 discloses the preparation of ball milled olefin polymerization catalysts in the presence of magnesium halide supports. Inorganic and organic diluents such as silica and polytheylene may be added during or after the ball milling step. These catalyst systems are intended for use in a low pressure gas phase fluidized bed process.
Catalyst systems prepared by these ball milling or micropulverizing procedures, with inorganic or organic support or diluent materials, however, have disadvantages with respect to the use of such catalyst systems in low pressure gas phase polymerization processes, and more particularly with respect to those catalyst systems that are to be used in a fluid bed process in that the morphology of these catalyst systems, i.e. their particle size and shape, makes them difficult to feed into the reactor in dry bulk form and also to fluidize them in the reactor. These feeding and fluidizing problems can lead to the formation of sheets and chunks of polymer in the reactor itself and/or in the gas recycle lines which can disrupt the continuous operation of the reactor due to the plugging of inlet, recycle, and outlet pipelines. The polymers produced with such catalysts are also likely to be of low bulk density due to an irregular particle shape and a relatively small particle size. These characteristics of such polymers can also contribute to the fouling of the reactor lines with sheets and/or chunks of polymer.
U.S. Pat. No. 3,515,684 discloses the preparation of fluidizable cracking catalysts by agglomerating, in a high speed bladed mixing device, very finely divided particles of a zeolite/water composition with an oily liquid. The resulting aggolomerated product is a dispersion, in oil, of zeolite particles of about 15-150 microns in size. These particles, however, have to be recovered from the oil and further processed before being used as catalyst materials in a cracking process.
U.S. Pat. No. Re. 28361 discloses the use of a high speed bladed finisher for the purposes of preparing masterbatchers of pigmented polymers, including polyethylene and polypropylene.
None of these references teach the use of a high speed bladed finishing device for the preparation of olefin polymerization catalysts that are particularly adapted for use in a low process gas phase polymerization process.
U.S. Pat. No. 3,990,993 discloses a process for depositing fine particle sized olefin polymer catalysts on web like submicroscopic fibrous structures of polymeric supports such as polytetrafluoroethylene and polyethylene, by the use of compressive shearing action in various types of mixing devices. No details are given with respect to the utility of such catalyst systems in a gas phase process. It would be expected that such supported catalyst systems would not be firmly supported on the polymeric webs and could be readily dislodged therefrom in a turbulent reaction medium such as in a gas fluidized bed process, and thus also produce operational problems due to polymer sheeting and chunking.